This invention relates to an improved manifold for a mixing device and, more particularly, to an improved manifold for a blender used to produce a slurry.
An important development in the production of oil and gas in recent decades, at least in the continental United States, has been the improvement of hydraulic fracturing techniques for stimulating production from previously uneconomically tight formations. For example, the largest gas field put on production in the lower forty eight states in the last twenty years is the Bob West Field in Zapata County, Tex. This field was discovered in the 1950""s but was uneconomic using the fracturing techniques of the time where typical frac jobs comprised injecting 5,000-20,000 pounds of proppant into a well. It was not until the 1980""s that large frac jobs became feasible where in excess of 300,000 pounds of proppant were routinely injected into wells. The production from wells in the Bob West Field increased from a few hundred MCF per day to tens of thousands of MCF per day. Without the development of high volume frac treatments, there would be very little deep gas produced in the Continental United States.
A blender, or blending unit, is an important piece of equipment in a large scale frac job because it produces the large quantity of slurry necessary, the slurry being a mixture of a liquid and the proppant. The liquid is typically water, although it is occasionally lease crude, diesel or other liquid, to which has been added chemicals to increase the capacity of the liquid to carry suspended solids. These chemicals are usually gelling agents that increase the viscosity of the water. The proppant used in frac jobs is normally sand of some type but is often a particulate material having more desirable properties, such as crush strength and the like. Thus, bauxite, alumina, carbo ceramics and other materials are often used.
Blenders are also useful in other operations, such as acid stimulation and water frac treatments which do not inject particulates into a well. In these situations, the blender is used for its ability to accept liquid from multiple sources and deliver it to multiple pump trucks.
All blenders are skid, truck or trailer mounted because the equipment is necessarily moved to each well site where the fracturing operation is conducted. In the United States, the maximum width of most blenders is accordingly dictated by highway regulations. Thus, without special permits to drive wide loads on highways, the maximum width of blenders is currently eight feet, six inches. Few service companies and few operators want a blender that is not driveable on paved roads without special permits because permits are time consuming and aggravating to obtain and sometimes emergencies require the blenders to move without prior notice.
Prior art blenders have a suction manifold providing a multiplicity of inlets for connection to one or more frac tanks holding the liquid, a hopper into which the proppant is delivered, a proppant metering system, a pump connected to the suction manifold and delivering liquid to one or more mixing chambers, a discharge pump and a discharge manifold for connection to one or more pump trucks which pump the slurry into the well. The suction and discharge manifolds have uniformly been round pipes, usually positioned on opposite sides of the blender vehicle.
Disclosures of general interest relative to this invention are found in U.S. Pat. Nos. 1,694,574; 3,563,475 and 6,095,429.
A blender of this invention provides an improved suction manifold providing lower pressure losses, less turbulence and higher throughputs than prior art suction manifolds. The same design may also be used for the discharge manifold.
The suction manifold comprises rectangular tubing having a length dimension preferably extending in the direction of travel of the trailer, truck or skid. The short dimension of the rectangular tubing is more-or-less horizontal, extending across the width of the blender vehicle providing a substantial space savings. The long dimension of the rectangular section is upright, i.e. more-or-less vertical.
Two additional important features are provided by a manifold design of this type. First, the vertical side of the rectangular tubing provides a large flat surface to which is welded a large number of flanges or other suitable inlet/outlet connections. It is much easier and less expensive to weld connections to a flat surface than to a circular one. This allows a large number of temporary conduits, such as flexible hoses, to connect to a large number of frac tanks or pump trucks while allowing the inlets and outlets to be spaced farther apart. This allows sufficient room around the inlets and inlet valves or outlets and outlet valves for connecting and disconnecting the hoses. More importantly, the throughput through the suction manifold of this invention is considerably greater than through a prior art suction manifold of a larger horizontal dimension.
It is an object of this invention to provide an improved manifold for a liquid mixing unit.
It is an object of this invention to provide a blender having an improved suction assembly.
Another object of this invention is to provide a blender having a suction manifold made from a length of rectilinear tubing.
A further object of this invention is to provide a blender having a discharge manifold made from a length of rectilinear tubing.
These and other objects of this invention will become more fully apparent as this description proceeds, reference being made to the accompanying drawings and appended claims.